This invention relates to the aerodynamics of a mobile vehicle, specifically the gap between a powered vehicle and pulled trailer. Examples would include a tractor-trailer heavy-duty truck and a towed mobile home. The gap between a tractor and trailer plays an important role in the overall performance the system during a cross wind. It affects drag as well as the handling quality of the vehicle and trailer combination.
In the prior art there have been attempts to close up the gap between the rear of the tractor and the front of the trailer. None of these was too practicable. An example is shown in FIGS. 1 and 2. The cab 201 of the tractor-trailer has side extenders 204 which extend to cover the gap 203 between the cab 201 and the trailer 202. Other prior art concepts included changing the shape of the front of the trailer to reduce overall aerodynamic drag. U.S. Pat. Nos. 4,021,069 and 4,702,509 are examples of this approach.
What is needed and does not exist in the prior art is a tractor-trailer system that uses crosswind to its advantage to form a low pressure zone relative ambient in the region between the tractor and the trailer in order to reduce aerodynamic drag.
An object of the invention is to provide a tractor-trailer system that uses crosswind to its advantage to create preferred pressure field in the region between the tractor and the trailer in order to reduce aerodynamic drag.
The tractor-trailer system of this invention uses aerodynamic principles to use crosswind to its advantage. The system has a curvilinear duct by attaching a convex body on the trailer front and a concave body on the back of the cab. When a cross wind enters the gap, it creates a negative pressure (compare to ambient) on the convex surface (trailer front) and a positive pressure on concave surface (back of the cab). Both of these pressures will help reduce the drag. Further having the crosswind flow smoothly can lead to less turbulence intensity in the gap, which can help in improving handling qualities of the system. There is a similar situation both for drag as well as handling qualities can be given for the air traveling in vertical direction (even at zero cross wind).